Testing Third-Party API Failures and Timeouts

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Failure Modes to Simulate

• Timeout from external API
• 5xx response from provider
• 429 rate limit
• Invalid payload shape
• Partial success (one request succeeds, next fails)

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Route Stubbing Pattern

import { test, expect } from '@playwright/test';

test('shows fallback when maps API returns 503', async ({ page }) => {
  await page.route('**/maps-provider/**', async (route) => {
    await route.fulfill({
      status: 503,
      contentType: 'application/json',
      body: JSON.stringify({ error: 'service unavailable' }),
    });
  });

  await page.goto('/locations');
  await expect(page.getByText('Map unavailable')).toBeVisible();
  await expect(page.getByRole('button', { name: 'Retry' })).toBeVisible();
});

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Timeout Example

test('shows timeout state for slow provider', async ({ page }) => {
  await page.route('**/credit-check/**', async (route) => {
    await new Promise((r) => setTimeout(r, 15000));
    await route.fulfill({ status: 504, body: 'timeout' });
  });

  await page.goto('/apply');
  await expect(page.getByText('Request timed out')).toBeVisible();
});

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Assertions That Matter

• User sees actionable message, not generic failure.
• Retry works and does not duplicate side effects.
• App remains responsive while waiting.
• Error is logged with enough metadata for support/debugging.

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Stably Features to Use for Resilience Monitoring

• Run resilience suites on Stably Cloud with high parallelism to cover multiple providers quickly.
• Add Scheduled Test Runs for recurring synthetic outage drills.
• Configure Alerts & Notifications so third-party regressions are surfaced before customers report them.
• Use run artifacts in Test Results to inspect traces, screenshots, and failure context when fallback behavior breaks.